Blecher, in a letter to NBC executive vice president and general counsel Rick Buchanan, said that "no punishment is warranted" against Sterling, and that he did nothing wrong. "We reject your demand for payment," the letter continues.

The NBA banned Sterling for life after a recording surfaced of him telling his then-mistress, V. Stiviano, that he did not want her bringing black people to his team's games. Sterling was also assessed the $2.5 million fine and ordered to sell the team.

In his letter, sources told SI.com, Blecher told Buchanan that Sterling did not violate any articles of the NBA constitution, specifically Article 35, which governs player misconduct.

But the NBA is expected to argue instead that Sterling violated the NBA's rules that bar owners from violating contractual obligations that include not engaging in unethical conduct or taking positions that are adverse to the NBA's standards.

Further, Blecher said in his letter that Sterling's "due process rights" were violated when the NBA banned him.

However, the NBA is a private association and not a legal organization or federal agency, so it may not be required to provide due process rights.

But a lawsuit could be an uphill battle, says SI.com, as Sterling has apologized for his statements and admitted in his CNN interview with Anderson Cooper that he "made a terrible, terrible mistake."

The NBA also will likely argue that Sterling's ban was due to the impact of his conduct. It not only triggered a player boycott, but caused the Clippers to lose sponsors and led to criticism from President Barack Obama — whose remarks Sterling called "flippant."

Blecher, who is in his 80s, is familiar with lengthy battles in the sports world. He served as the lead attorney for the Los Angeles Memorial Coliseum in successful antitrust litigation against the NFL over the Raiders' relocation from Oakland to Los Angeles, and is one of the few attorneys who has defeated the NFL.

Los Angeles Clippers owner Donald Sterling is not walking away from the NBA without a fight, and he won't be paying its $2.5 million fine, his new lawyer says in a letter. Instead, the disgraced team owner plans to sue the NBA, Sterling's attorney, powerful antitrust...